The present invention relates generally to electric energy remote metering and data recording systems and more particularly, to methods and apparatus for detecting the occurrence of a system malfunction and enhancing the preservation of reliable and verifiable metering data collected from remote metering locations.
Electric utilities frequently use data recorders (generally referred to as demand or load profile recorders) for monitoring energy consumption as measured by a meter connected to a consumers load. Typically, these recorders are designed to record electrical pulses proportional to energy consumption which are provided to the recorder by a pulse initiator in the meter. Modern day electronic recorders are designed to transmit the recorded data to a central computer, via telephone lines, to enable the utility to process the data to bill the consumer according to his energy consumption. One such type electronic recorder is disclosed in U.S. Pat. No. 4,639,728. Another similar recorder is disclosed in U.S. Pat. No. 4,439,764.
Utilities also use the transmitted data for; (i) conducting load surveys for load management purposes, (ii) profiling of a consumers energy consumption, and (iii) the collection of data to justify rate modifications.
Recorders of the above type are ideally suited for use in meter installations which are widespread or not easily accessible. These recorders may also be used in installations where a utility wants to simultaneously monitor large numbers of meters throughout a utility power network, or several meters located at a large energy consumer account such as a commercial or industrial user. Because the accumulated metering data is to be used for billing and other purposes as set forth above, utilities want to be assured that the collected data does not get lost and that it is accurate and verifiable. An abnormality, such as a malfunction in the power generating system or in the metering or recording equipment, can cause the loss of valuable revenue or survey data. Thus, immediate notification of a malfunction is another requirement. In order to achieve these assurances, means must be provided to detect the presence of a malfunction and to protect against the loss of revenue and load profile data in the recorder and to further verify that the protected data is valid. To appreciate how a remote metering system of the type contemplated by the present invention may be used to provide the above assurances, it is considered advantageous to briefly describe how meters and their associated registers have been used in remote metering and data recording systems.
It is well known that watthour meters, and similar types of meters, contain a register or registers for accumulating and displaying various quantities of energy consumption, such as total kilowatt-hours, watthour demand, etc. The conventional induction watthour meter, with rotating disc and shaft, contains a mechanical register (driven by a gear on the shaft) which continuously displays the total accumulated kilowatt hours consumed. Switch or clutch activatable mechanical demand and time of use registers are also used on these meters to display demand and time of use quantities (ie, the amount of energy consumed over a predetermined time of use period or a specified time interval within a time of use period).
In recent years, micro processor based electronic registers have been developed for use on conventional watthour meters to accumulate pulse data proportional to power consumption. This pulse data is usually provided to the register from an optical pick up or sensor device which senses meter disc rotation. These registers come in varying degrees of sophistication, and have the advantage that they can perform calculations on accumulated pulse data and electronically display much more information than is possible with a conventional mechanical type register. A pulse initiator device is also frequently used in conjunction with an electronic register to provide relay contact (form A and C) pulses proportional to power consumption to an external recorder of the type contemplated by the present invention. The pulse initiator device is driven by pulses from the electronic register. The pulse initiator can be either an integral part of the register or separate therefrom.
When it is desirable to provide relay contact pulse data to a recorder from a meter which does not have an electronic register, a separate pulse initiator is usually installed adjacent to or in the meter. In this instance, the pulse initiator receives its input data pulses directly from the optical pick up device in the meter.
When electronic registers are used, a major concern to the utilities is that a system failure or equipment malfunction, if left undetected for a sustained period (such as a month, between meter readings) can cause a significant loss of valuable revenue data. Typical problems which cause a loss of revenue data are, power line or transformer failures, loss of power to the electronic register or a malfunction in the electronic register or optical pickup device. In addition, when a recorder is used to record pulse data, any system failure or malfunction which disrupts the pulse initiator output pulses from the meter can result in the loss of data being fed to the recorder. This loss of recorder data is particularly critical, because that data is also used by the utilities to bill consumers. The present invention substantially reduces the possibility of losing this recorder data. The invention also provides the capability to minimize the loss of data in the electronic meter register by quickly detecting and indicating the presence of a system abnormality affecting the register performance. Such indication allows the utility to take immediate action to correct the abnormality.
To partially satisfy the above concern, electronic registers have been teamed with conventional mechanical type registers on conventional induction type watthour meters. This teaming of registers provides a certain amount of verifiable back up data for the utilities not otherwise available. For example, if an electronic register fails, or fails intermittently to collect data, and all or part of its data is lost, the mechanical register will preserve at least that part of the meter data duplicated on the mechanical register. Mechanical registers are very reliable. However, if the mechanical register fails, the electronic register will provide the necessary backup data.
From the foregoing, it can be seen that, at best, the teaming of an electronic register with a mechanical register provides a means of protecting against the loss of only a portion of the meter data when the electronic register fails. Furthermore, in the case of a recorder, loss of pulse data from the meter can result in the non-recording of valuable revenue data during that period of time that data pulses to the recorder are interrupted. This can result in the recording of invalid or incomplete data unless means is provided to ensure that the data which gets recorded is as valid as possible. Thus, it can be seen that a need exists to protect against the loss of recorder data in the event of an abnormality in the metering system which causes a disruption in the pulse data signals to the recorder. In addition, a need exists to quickly notify the electric utility of a system abnormality and to provide assurance that the protected data is valid and verifiable.
The aforementioned U.S. Pat. No. 4,639,728 discloses a system for verifying meter data provided to an electronic recorder. That system employs a conventional watthour meter having a mechanical register for registering total kilowatt hours. A pulse initiator in the meter generates KYZ relay contact output pulses. The KYZ pulses are provided to a micro processor based electronic demand recorder. These pulses are accumulated by the recorder over a number if successive intervals to make up a record. An encoder in the meter can be interrogated by the recorder. The encoder permits reading of the mechanical positions of the dials on the meter register into the recorder. At the end of the aforementioned record, the register dial positions, as indicated by the encoder, are read and stored by the recorder. The accumulated KYZ pulse data and the encoded register data are compared. If there is an acceptable correlation between the accumulated pulse data (KYZ pulse count) and the encoded register data (dial reading), the pulse data accumulated during the several successive intervals of the record are deemed verified.
The use of an encoder for the verification of pulse data as disclosed in the above mentioned patent has disadvantages and limitations. One disadvantage is that the encoder cannot provide full back up (redundant) data to support the KYZ pulse contact data that might get lost or corrupted due to a system abnormality or malfunction. Since an encoder is read to provide a single reading of the register dials only at the end of a lengthy record, the encoder data is useful only to determine that no error has occurred in the KYZ pulse data recorded since the last encoder reading. If an error is detected, then the recorded pulse data is suspect and thus considered invalid. Since the encoder does not provide any duplicate back up data to support the invalid KYZ pulse data, the latter data is, for all practical purposes, lost because it is unusable for billing purposes. As a result, the only useable revenue data left is the total kilowatthour reading from the meter dial encoder.
Another disadvantage of dial encoders is they cannot be used in fully electronic watthour meters. This is due to the fact that these types of meters contain fully electronic registers instead of the conventional mechanically driven registers. Thus, an encoder is precluded from use in reading an electronic register. Examples of fully electronic watthour meters are disclosed in U.S. Pat. Nos. 4,535,287 and 4,556,843. These patents are assigned to the assignee of the present invention.
From the foregoing, it is clear that a need exists for a recorder system having universal application with all types of watthour meters (electronic and induction) and which protects against the loss of recorded meter data and which further promptly detects a system abnormality affecting the recording of such data. The present invention is directed toward fulfilling these needs as set forth in the following description of the invention.